The total number of all housing units is a statistic derived from the Housing Vacancy Survey, which is a supplement to the Current Population Survey.

A housing unit is a house, an apartment, a group of rooms, or a single room occupied or intended for occupancy as separate living quarters. Separate living quarters are those in which the occupants do not live and eat with other persons in the structure and which have direct access from the outside of the building or through a common hall.

Number of Housing Units in Structure. A structure is a separate building which either has open space on all four sides or is separated from other structures by dividing walls that extend from ground to roof. In double houses, row houses, and houses attached to nonresidential structures, each building is a structure if the common wall between them goes from ground to roof. Sheds and private garages which adjoin houses are not counted as separate structures. In apartment developments, each building with open space on all sides is considered a separate structure. The count of housing units in a structure is the total number of units in the structure, both occupied and vacant units. In the tabulations, occupied mobile homes or trailers, tents, and boats are included in the category one housing unit in structure.

Foreclosures may be in any of the housing stock categories on Table 3 (Estimates of the Total Housing Inventory for the United States) of the press release. They could still be occupied by the owner, or still be occupied by the renter, making them "owner occupied" or "renter occupied", respectively.

They could also be vacant and available for sale or for rent. If the unit is classified as "vacant for sale only", it will be included in the "vacant for sale" category. If the unit is for rent or "for sale OR rent, " it will be included in the "vacant for rent" category.

Many foreclosures will be in the "vacant other" category, because they are neither for sale or for rent - they are still in the foreclosure process and tied up in legal proceedings, or being held off the market until the legal owner of the property decides what to do. In addition, it is possible the unit could be undergoing repair for future use. Also included in the "vacant other" category are units "for occasional use" and units "temporarily occupied by persons with usual residence elsewhere", both of which may contain foreclosures. Foreclosures could also be included in the seasonal category, depending on the specific situation.

In conclusion, foreclosed properties may appear in all of the housing unit categories, not just the "vacant for sale" category

Geographic regions. The four major regions of the United States for which data are presented in this report represent groups of States as follows:

Northeast: Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, Vermont, New Jersey, New York, Pennsylvania.

Midwest: Illinois, Indiana, Michigan, Ohio, Wisconsin, Iowa, Kansas, Minnesota, Missouri, Nebraska, North Dakota, South Dakota.

South: Delaware, District of Columbia, Florida, Georgia, Maryland, North Carolina, South Carolina, Virginia, West Virginia, Alabama, Kentucky, Mississippi, Tennessee, Arkansas, Louisiana, Oklahoma, Texas.

West: Arizona, Colorado, Idaho, Montana, Nevada, New Mexico, Utah, Wyoming, Alaska, California, Hawaii, Oregon, Washington.